1. Field of the Invention
The present invention relates to a method of and an apparatus for coating a photoresist film over a wafer in the lithography process for the fabrication of semiconductor devices, and more particularly to a method of and an apparatus for coating a photoresist film over a wafer, capable of eliminating local non-uniformity of the photoresist film possibly caused by the topology of the wafer and uniformly controlling the thickness of the photoresist film.
2. Description of the Prior Art
In the lithography process for the fabrication of semiconductor devices, generally, the formation of a photoresist film over a wafer is involved. The formation of such a photoresist film is carried out by coating a photoresist material, which consists of photoresist particles dissolved in a solvent, over a wafer while rotating the wafer by use of a nozzle.
However, this injection method has a problem that the thickness of the photoresist film coated on the wafer is locally non-uniform when the photoresist material contains photoresist particles of wide grain size ranges. Although the photoresist particles of a small grain size have little effect on the uniformity of the coated photoresist film, those of a larger grain size have a considerable effect on the uniformity of the photoresist film, thereby making it impossible to form a uniform pattern.